The effects of arterial free fatty acids on myocardial oxygen consumption have long been debated. In the literature toxic effects of free fatty acids on myocardial contractility have been reported. Also, elevated free fatty acids are associated with arrhythmias and a higher complication rate following acute myocardial infarction. The major emphasis of this project will be to determine if myocardial utilization of free fatty acids is associated with an increased myocardial oxygen consumption. To determine myocardial utilization of free fatty acids, C14-l-palmitic acid and C14-l-oleic acid will be infused and 14C02 will be measured in the coronary sinus. This will be performed in young male volunteers and patients with ischemic heart disease both at rest and during the stress of atrial pacing. Heparin or nicotinic acid will be infused intravenously to elevate and lower arterial free fatty acids respectively. The selectivity of the myocardium for individual free fatty acids will be determined. The effect of free fatty acids on myocardial extraction of other substrates will also be assessed.